1. Field of the Invention
This invention relates to steel gratings of the type normally used for area ways, floor and sidewalk openings, platforms, stair treads and the like.
2. Description of the Prior Art
Prior structures of this type usually employ an assembly of bearing bars or flat metal plates held in spaced parallel relation by a plurality of cross bars welded cross wise of the bearing bars at or below the upper surfaces of the bearing bars, as for example in U.S. Pat. No. 2,656,903. Upon occasion edge frames are attached to the ends of the assembled bearing bars and cross bars by welding the same thereto to complete the grating.
This invention eliminates the welding heretofore believed necessary in forming such steel grating structures, avoids the warpage commonly found in such welded structures as a result of heat distortion and provides a more economically formed steel grating.